Loudspeaking, or hands-free telephones, have achieved widespread acceptance in the commercial environment. Such telephones are convenient for conducting multi-party conversations when several people are gathered in one office. Another particularly convenient feature of the loudspeaking telephone is that the user may converse without actually being in contact with the telephone, except possibly to initially answer an incoming call.
Typically, such loudspeaking, or as they are also called, speakerphone, telephones require a source of power to control the internal logic as well as to drive the loudspeaker. In addition, such telephones employ inductors and transformers in order to balance the impedance between the telephone line and the loudspeaker. This unbalance condition results because loudspeakers are inherently low impedance devices while the telephone line requires a much higher impedance for proper power transfer. It follows then that problems arise in situations where it is desired to utilize the convenience of a speakerphone at a low cost, without bulky inductors or transformers and without external power. These problems are compounded when it is remembered that as loop length changes the line impedance as well as the available power changes.